constant ActionView::Base::Subclasses::MainController not defined

Dear all,

Today I've just checked-out Rails version 3 and when I have generated
scaffold, and open my apps from the browser, I encountered this error:
NameError in MainController#index

constant ActionView::Base::Subclasses::MainController not defined

Where do I defined this constant?

Does anybody have a clue? I'm still new with Rails 3.

Thanks for your assistance.

Regards,

Where did you get this "version 3" ? As far as I know it's not been released.